The invention relates to optical bar code readers, and more particularly to stationary bar code readers with multiple apparent source scan geometry.
Typical scanning devices for bar code readers of the prior art, particularly POS (point of sale) scanners, have consisted of three separate die cast parts. To assemble these three castings together generally required special assembly tooling which would locate a relatively large number of connection points relative to additional connection points, between castings. Precision in such assemblies is required in order to achieve uniform and consistent scan geometry.
In general, two methods have been employed in the past for assembly of such castings in POS scanners. One method involved machining and pinning castings together, while another involved shimming various connection points to compensate for casting variations. Either method amounted to a costly and time consuming process in comparison with the present invention.
Partitioning of an optics cavity in scanners of the prior art has usually been accomplished by fitting at least three separate castings together. The fits need to be extremely uniform to assure sealing integrity, as well as to verify that the three castings have been assembled properly.
In prior POS or similar type scanners, there were sometimes included a number of adjustable mirrors, such as six, by which the scan geometry was achieved. The mirrors were required to be adjusted so that desired scan segments would pass accurately through slotted insert apertures in the deck of the scanner. To achieve the required adjustments, there were often included a large number of spring clips and set screws accessible from the outside of the assembled scanner. Such adjustments comprised the second of two alignment sequences for such scanners.
Mirror attachment techniques according to prior practice require some flexibility in adhesives used to hold the mirrors in place and to provide mechanical hinges. Because of multiple alignment iterations involved in these prior mirror attachment procedures, the cure times involved with the bonding agents between succeeding steps could appreciably slow the assembly process.
For universality of application, POS scanning devices require multiple interfaces to other POS equipment, as well as four different power options for different geographical areas of the world. To provide different interfaces requires unique interface boards and cabling which have been accessible only with considerable disassembly in most prior scanners. Changing of interfaces has often required that various covers and voltage shields, as well as the main circuit board, be removed before access to the interfacing printed circuit board can be made. The various connectors have needed to be disconnected.
In deck tops of many prior POS type scanners, a plastic top cover was used on the deck in connection with an upper plastic window. Moisture seals are required for the optics cavity, including at this upper plastic window. When the plastic window requires replacing, this was usually not capable of accomplishment by the user while still maintaining the moisture seal. Further, the plastic windows have been vulnerable to scratches caused by items coming into contact with the window, even through slotted inserts. Scratching will greatly diffuse and attenuate the beam, reducing efficiency and reliability, so that plastic windows of prior scanners have often required relatively frequent replacement.